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5 GT Turbo Unstable rough idle

Miguel

New Member
I rebuilt the engine some months ago, rebuilt the carb too. But since the rebuilt the engine runs unstable at idle. I have to keep rpm above 2000rpm so the engine keeps running. When I try to reduce the idle it enters into a cycle where it goes up to 2200-2000rpm and down to 1600-1400 rpm and repeats. I posted a video running this cycle for reference () In the video you can see the afr readings. The idle screw seems to have no effect on the mixture/afr, readings do not change with idle screw. What is it ? :grin.gif::search.gif:It is driving me crazy.

I have checked many things but I will probably check them again following your recommendations....

Thanks all
 
Throttle stop is set too high and the mixture is too lean for whatever reason. Knock the throttle stop down and fix or adjust mixture, it could be blocked idle jet, air leak etc.
 
I agree with you, when I tried to close the throttle before the engine does not start. I will try what you say and before I will remove the idle jet and blow it in case the idle circuit is blocked somewhere.
 
Update: I removed the carb cleaned thoroughly in warm water cleaning machine, plenty of carb cleaner. Rebuild it, closed the throttle, etc. It improved but it is still no ok. The improvements can be seen in the afr as now closer to 21 (too lean) and not much hesitation. I changed and added hose clips to all vacuum hoses. There is something still not fine because after a while it start to do crazy things, like jumping rpm again and entering the cycle I described before.
I bought another carb body, cleaned it, new main jet. I will try it over the weekend again and provide a further update.
I wish there was a cheap EFI-bolt on system!
 
If you've used a rebuild kit, check the washer on the idle jet holder, It's probably a long time since I did one, but remember replacing a washer with a new one from the kit which was thicker, which stood it off, can't remember whether it made it lean or rich, just ran like a sick pig.............I only understand carbs and their workings when I'm actually at them.......after that it all seems to fade to fogginess...........
 
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